The influential book IQ and the Wealth of Nations has lots of interesting data. But it does not say much on reasons for the IQ differences it identifies. What is said is that IQ is primarily inherited from one's parents, and that what a child eats also plays a role.

1. Immigration seems to have a sorting effect on IQ. In the book IQ and the Wealth of Nations the national average IQ for China is 100. But IQ's for countries where large numbers of Chinese have migrated are noticeably larger (Hong Kong 107, Taiwan 104, Singapore 104). Perhaps individuals who migrate to (and remain in) a different country are smarter on average than their former neighbors who stayed at home.

2. Certain East Asian countries have the highest average IQ scores, particularly in mathematical/ spatial skills. This talent may develop because students in China, Korea, and Japan are required to recognize and utilize thousands of word characters. It's interesting that Japanese living in the US (who are taught in English ) score about 3 IQ.points less than their countrymen in Japan. This IQ difference is the opposite of the Chinese immigrants in point 1, who do learn to write in Chinese characters in Singapore. Click for outside

4. Jews in the US and Europe have some of the highest average IQ's in the world -

around 112, some observers claim. With centuries of pogroms, ending in the World War II holocaust, Jewish populations in Europe have been repeatedly culled. It is not unreasonable to speculate that many smarter European Jews, including those families who had been successful in making money, were also more successful on average in escaping with their lives.

5. The average IQ in Israel of 94 may not be so surprising, on second look. In contrast to European Jews, the Jews of Middle Eastern and North African heritage test much lower on IQ. Israel combines both regional origin Jews in roughly equal numbers. It also has a large and rapidly growing number of Palestinian Arabs (compare the average IQ in Egypt of 83). Thus it many not be surprising for the mixed population in Israel to have an average IQ of 94.

6. In world averages, the US has the highest national income, but an IQ average of only 98. US IQ isbelow that of many other countries, including relatively poor China. Like Hong Kong, Taiwan, and Singapore, the US is largely a country of immigrants, and average IQ in the US may well be higher than in many of the countries from which the migrants came (as from Latin America). But along with a sorting of IQ levels, immigration may also favorably select those with greater ambitions. Research indicates that ambition may play an even greater role in individual financial success than IQ.

7. Current US border enforcement procedures may contribute to the economic strength of the US. On one hand, high IQ individuals outside the US are encouraged by employers here to get US work visas.On another track, the semi-porous border with Mexico tends to select for desirable workers.On average, the migrants with greater ambition and above average IQ are able to foil the US border protection systems. As in point 1 above, the average IQ of Mexican-Americans is greater than the average IQ in Mexico.The net result is that the pool of talented workers in the US grows, to the detriment of their native countries.One drawback might be the feisty youth gangs in Los Angeles and other barrios of illegals. But the overall benefits of an inflow of ambitious talent filtered illegally into the US likely far exceed such drawbacks.

8. In the past, the opposite of voluntary migration to another country was slavery. Nations like the US and Brazil were peopled with both types of migrants. Accordingly, opposite selection effects for the free and slave peoples were at work. On average, those arriving voluntarily (including indentured servants) likely had more ambition and brains than those who were caught and sent as slaves. The migrations into the US of both Eastern European Jews and Africans were the result of horrible events. Many people died in these events, especially in the originating countries. One process selected out people with higher IQ's and ambition, the other possibly the opposite. Thus we should not be surprised at the large difference in IQ's currently between these groups in the US. See: IQ and success for Blacks

After writing the above, I discovered these relevant comments on http://www.rlynn.co.uk - Richard Lynn's website. The last paragraph is the same idea as Sloan's in item 3 above:

My major discovery is that the Oriental peoples of East Asia have higher average intelligence by about 5 IQs points than Europeans and peoples of European origin in the United States and elsewhere. I first published this finding in 1977 in a paper on the intelligence of the Japanese. In subsequent years the high Oriental IQ has been confirmed in numerous studies of Oriental peoples in Hong Kong, Taiwan, South Korea, China, Singapore and the United States.

The theory I have advanced to explain these race differences in IQ is that when early humans migrated from Africa into Eurasia they encountered the difficulty of survival during cold winters. This problem was especially severe during the ice ages. Plant foods were not available for much of the year and survival required the hunting and dismembering of large animals for food and the ability to make tools, weapons and clothing, to build shelters and make fires. These problems required higher intelligence and exerted selection pressure for enhanced intelligence, particularly on the Orientals.

Viewer comment 11/3/04:"Thank you for creating the IQ section of your website. It's such a relief to find someone unafraid to post up the facts about the hereditary nature of IQ. It's unfortunate that the subject of a correlation between race and IQ is a taboo and "politically incorrect" subject in many academic circles, but you've managed to deal with it in a sensitive yet straightforward manner, and I applaud you for that."